The invention relates to alkaline earth metal alkylene diamides, a method for their production, and their use.
The alkaline earth amides are strong metallizing agents and serve as, among other things, as starting materials for the production of alkaline earth metal oxides (M. F. Lappert et al., xe2x80x9cMetal and Metalloid Amides,xe2x80x9d John Wiley and Sons, NY 1980).
The alkoxides (or alcoholates) of the alkaline earth metals find use, for example, as precursors for the production of thin metal oxide coatings (by the CVD or the sol-gel process) for electronic materials, especially high-temperature superconductors (W. A. Hermann, Angew. Chem. 1995, 107, 2371).
Alkaline earth alkoxides are also used as additives in the anionic polymerization of dienes with butyl lithium; here the addition of alkaline earth alkoxides brings about a high trans-content in the polymer, which has an advantageous effect on the properties of the end products, e.g. tires (U.S. Pat. Nos. 5,100,965, 4,020,115 and 3,992,561).
In addition, on account of their basic properties and often good solubilities in ethers and hydrocarbons, the alkaline earth alkoxides are also usable in many ways as reagents in deprotonization and alkoxylation reactions as well as condensations (D. C. Bradley, R. C. Mehrotra, D. P. Gaur, Metal Alkoxides, Academic Press, N.Y., 1978; U.S. Pat. No. 4,555,498).
Methods for the synthesis of barium alkoxides, for example, which have been known heretofore start out from
the metals:
Ba+2ROxe2x80x94H= greater than Ba(OR)2+H2xe2x80x83xe2x80x83(1)
the metal amides (the amide route):
Ba(NH2)2+2ROxe2x80x94H= greater than Ba(OR)2+2NH3xe2x80x83xe2x80x83(2)
the metal iodides (salt metathesis):
BaI2+2ROxe2x80x94K= greater than Ba(OR)2+2KIxe2x80x83xe2x80x83(3)
Reaction (1) is very slow and leads to xe2x80x9ccomplexesxe2x80x9d Ba(OR)2*(ROH)n which must be decomposed at high temperatures.
In Reaction (2) the metal is first dissolved in liquid ammonia (T less than xe2x88x9233xc2x0 C.) to form the amide and then successively to the alkoxide, which involves the disadvantages of a low temperature reaction.
Lastly, in Reaction (3) the production of the iodide is uneconomical.
The problem addressed by the invention is to overcome the disadvantages of the state of the art and prepare substances which permit the production of alkaline earth metal alkoxides by a relatively simple method.
The problem is solved by alkaline earth metal alkylene diamides, wherein Ba, Sr and Ca can be used as alkaline earth metals. Alkaline earth metal alkylene diamides can be easily reacted with an alcohol to form the corresponding alkaline earth metal alkoxide. Preferred alkaline earth metal alkylene diamides are derived from the primary alkylene diamines. Especially preferred are alkaline earth metal ethylene diamides.
Surprisingly it was found that the alkaline earth metals Ba, Sr and Ca can be dissolved very easily in ethylenediamine, whereupon the corresponding alkaline earth metal ethylenediamine and hydrogen are formed: 
Preferably the alkaline earth metal in the form of powder, granules or pieces is fed into the ethylenediamine. The reaction is preferably performed under an inert gas atmosphere. Preferably the ethylenediamine is added to the alkaline earth metal in excess at a molar ratio of 2:1 to 50:1. A preferred reaction temperature is between 8.5xc2x0 C. and 118xc2x0 C., i.e., in the range in which ethylenediamine is fluid. In principle the reaction can also be performed at lower temperatures with solid ethylenediamine, as a solid state reaction, or at higher temperatures with gaseous ethylenediamine. Especially preferred is the temperature range of 10 to 40xc2x0 C.; the reaction can also be performed advantageously at room temperature. A measure of the reaction rate is the evolving of hydrogen. The reaction rate of the exothermic reaction can be controlled by the rate of addition of the alkaline earth metal and to a limited extent by cooling the reaction vessel. The alkaline earth metal ethylene diamide precipitates as an insoluble, gray solid which can be isolated by filtration and/or concentration and drying.
The reaction can best be performed with barium as the alkaline earth metal and ethylenediamine as the alkylenediamine.
Basically, the reaction can also be performed with alkalinediamines other than ethylenediamine; of course the reaction rates in this case are slower; for example, several days are required at the boiling point at standard pressure to dissolve barium in propylenediamine (to form the barium propylenediamide). Acceleration of the reaction can be achieved by raising the temperature and simultaneously raising the pressure.
One application of the alkaline earth metal akylene diamides is their use in the synthesis of alkaline earth metal alkoxides.
For this purpose the alkaline earth metal alkylene diamides (here an alkaline earth metal ethylenediamide) is reacted with an alcohol to form the corresponding alkaline earth metal oxide. 
Preferred in that case is a stoichiometric amount of alcohol: nonstoichiometric amounts of alcohol lead to the desired product plus complex compounds. The reaction with alcohol can be performed undiluted, in residual excess alkylenediamine or in a solvent. The solvent can be aliphatic hydrocarbons (cyclic or acyclic) with 5 to 12 carbon atoms or aromatic hydrocarbons with 6 to 12 carbon atoms and/or ethers.
The hydrocarbons can be, for example, one or more of the compounds pentane, cyclopentane, hexane, heptane, octane, cyclohexane, toluene, xylene, cumene, ethylbenzene or Tetralin.
The ethers can be, for example, one or more of the compounds, tetrahydrofuran (THF), 2-methyl-THF, tetrahydropyran, diethylether, diisopropyl ether, dibutyl ether, dioxane, methyl-tert.butyl ether, glycol ethers (such as monoglymes, diglymes) or mixtures thereof.
An isolation of the alkaline earth alkoxide can be performed by concentration by evaporation and drying, in which case the alkylenediamine can be recycled. The alkaline earth alkoxide can be prepared either as a solid or it can be dissolved in a solvent and offered as a ready-to-use solution.
The invention is further explained below with the aid of examples.